Gaseous electric discharge lamp device



Patented Dec. 21, 1937 UNITED STATES PATENT OFFiCE Hans Alterthum,

Lompe, Berlin, Germany,

Berlin-Wilmersdorf, and Arved assignors to General Electric Company, a corporation of New York No Drawing. Application July 6, 1937, Serial No.

152,270. In Germany July 10, 1936 1 Claim.

The present invention relates to gaseous electric discharge lamp devices.

The object of the invention is to provide a gaseous electric discharge lamp device which does not require an external resistance. Another object of the invention is to provide a method of operation for a gaseous electric discharge lamp device whereby the device is in effect selfballasting. Still further objects of the invention will be apparent from the following description thereof and from the appended claim.

Electric illuminating tubes in order to burn in a stable condition hitherto have always required an external resistance with a rising characteristic, because they themselves have a falling currentvcltage characteristic, 1. e. because, with an increase of the current strength, the voltage taken up by the tube drops; this namely results in the fact that, with an accidental increase of the current strength, the internal resistance of the tube is diminished strongly more and more, so that the supply line is practically short-circuited. The external resistance, provided it is chosen sufficiently large, has the efiect that the total characteristic of the tube and the resistance becomes a rising one, so that a current rise is limited by the then ensuing voltage rise. The external resistance therefore represents an additional device which hitherto has been indispensable for illuminating tubes, and which aside from its initial cost also impairs the performance of the tube because of its own wattage consumption.

Therefore one has already attempted to dispense with the external resistance. For this purpose it has most often been proposed to so change that part of the discharge which occurs in the cathode fall that it has a rising characteristic which outweighs the drop of the characteristic of the remainder of the discharge, namely the positive column.

The methods used for this purpose have been various, most often they aim at making the socalled normal cathode drop anomalous, because, concerning the latter it is well known that it itself has a rising characteristic. In practice however it is very diflicult, and especially with the hot electrodes which are necessary for carrying greater loads it is hardly possible to make the cathode fall sufiiciently anomalous, in view of the fact that, with an increasing tube length, the drop of the characteristic of the positive column becomes ever stronger.

With tubes according to the invention therefore the course is followed of making the characteristic of the positive column itself a rising one, and indeed so strongly rising that thereby, at the same time, those parts of the discharge which lie in the electrode fall regions and have falling characteristics are also taken into account to such an extent that the characteristic taken at the ends of the tube is entirely rising.

The reason for the falling characteristic of the positive column, as is well known, consists in the fact that, with an increase of the current strength, the number of electrically charged particles increases, whereb as a result of the reduction of the internal resistance of the column, the gradient of the latter, therefore thevoltage drop per cm. of tube length, becomes smaller. The invention proceeds from a recognition of the fact that in the positive column of a gas mixture or gas-vapor mixture, with an increase of the current strength, aside from the above mentioned increase of electrically charged, particles, still another process occurs, which, if it were to occur alone, would increase the gradient of the column. This process is the inherently well known electrophoretic wandering to the cathode of the more easily ionizable filling component, for instance mercury in neon, sodium in argon, argon in helium, as it occurs under the influence of a direct current or of an asymmetrical alternating current feeding the tube. This electrophoresis in the gaseous mixture is described in co-pending application Serial Number 113,919, filed December 2, 1936 to which application reference is had for a disclosure of a device of a type which is operable by the method of the present invention.

This electrophoretic wandering leads in general to a concentration-drop of the two filling-components which sets in along the tube. The degree of this concentration-drop depends, aside from the electro-phoresis which furthers it, on the diffusion-tendency of both filling-components which works in the opposite direction. The condition which sets in corresponds to the equilibrium of both forces, its variability corresponds to the displaceability of this equilibrium. With a displacement of this equilibrium by an increase of the current strength, a steeper concentration-drop and with it a rise of the voltage consumption takes place. This fact has never been sufficiently noticed heretofore, since with customarily operated tubes, the voltage decrease which was caused by an increase of the electrically charged particles during a rise in the current strength, was much greater than the simultaneously occurring voltage increase caused by the increased steepness of the concentration-drop.

The invention accordingly is based on the fact that an electric illuminating tube filled with a gas mixture or a gas-vapor mixture, while being fed with direct current or with an alternating current which is made asymmetrical in the tube itself, is adjusted for such a current strength that'the concentration-drop of the filling-components which is caused by electrophoresis during an increase of the current strength becomes considerably steeper and therefore the voltage consumption is also considerably increased, and indeed to such a degree that it outweighs the voltage decrease which is caused in the column by the simultaneously occurring increase of the electrically charged particles, and in a'given case also the decrease of the electrode drops. A joint consideration of the electrode drops is necessary in case they themselves have a falling characteristic, as is always the case with hot electrodes, but on the other hand not in the case of electrodes with a sufliciently anomalous cathode drop. Thereby the characteristic of the entire tube becomes a rising one, so that the tube can be operated without an external resistance or only with a smaller external resistance than otherwise. 7

A suflicient increase of the concentration-drop= of the filling-components during ariseof the current strength can be achieved in several ways. Here all those media Work favorably which hinder the thermal diffusion of the filling-components, as for instance, a sufficiently small tube cross section; furthermore all media which facilitate the electrophoretic wandering, for instance suflicient- 1y different ionization potential of the filling-components and suificiently high current densities of the direct current or of the direct current portion of an asymmetrical alternating current produced in the tube. The latter is converted from the symmetrical alternating current fed to the tube, for instance by the use of hot electrodes having variously strong emission capacity during operation, by the use of one hot electrode and one cold electrode, or if the tube is to have two cold electrodes, by the use of a high voltage transformer having an idling voltage which just reaches the ignition voltage of the tube, while at the same time, an especially sensitive spot of tube is grounded,'which spot is determined by experiment. It is of special significance for the produc-. tion of the desired concentration-drop of the filling-components, to make the concentration of the more easily ionizable component very small when compared with that of the other component, thus for instance, the concentration of the metal vapor when compared with a rare gas which is also present in the tube; In the case of a condensable filling-component, care must be taken that the desired concentration-drop is not disturbed by subsequent delivery from a base body. The most favorable concentration of the more easily ionizable component occurs most often with an amount which is just suflicient for light-excitation. Tubes according to the invention burn in one color over their entire length or also with two, longitudinally adjacent, different-colored lightcolumns, according to Whether, during operation, the more easily ionizable component is present in the whole tube or only in a part of the latter.

What We claimas new and desire to secure by Letters Patent of the United States is:-

The method of operating a gaseous electric discharge lamp device comprising a container, electrodes sealed therein and an atmosphere therein of a mixture of gaseous constituents having different ionizing potentials which method consists in the step of causing a greater current flow in one direction than in the opposite direction in the device and of such magnitude that the concentration-drop of the filling Which is caused by electrophoresis during an increase of the current strength produces a voltage increase which outweighs the voltage decrease caused in the column by the simultaneously occurring increase of the electrically charged particles and the decrease of the electrode-drops, so that the characteristic of the tube is a rising one.

HANS ALTERTHUM. ARVED LOMPE'. 

